Gear units having a shaft and attached gear are used in countless devices. Because of their high usage, manufacturers look for low cost methods of producing the gear units. However, it is difficult to produce a gear unit at a low cost that has high motion quality. Poor motion quality often causes the shaft to “wobble” on the shaft during rotation.
Many of the existing gear units experience poor motion quality caused by uniformity problems in one or both of the shaft and gear. For gears, the interior opening that receives the shaft is often the cause of the problems. Poorly constructed interior openings cause the shaft to not seat properly on the shaft. This is especially prevalent in embodiments having interior openings that become non-uniform during use.
Another problem occurs in connecting the gear to the shaft. One common manner of attachment is referred to as a press fit. However, when the stresses of the press fit load are applied, the gear deflects unevenly, especially when the interior opening is non-uniform. Another concern is the press fit assembly of the gear upon the shaft. Due to manufacturing variation as well as creep, press fits have been found to be unreliable in high volume manufacturing environments.
Further, the gear unit should be constructed in an economical manner. Gear units should not be outlandishly priced that it is not practical for use within the device. Improvements to the connection between the gear and shaft should add to the performance of the device, but not at a price that will prevent its use.